Insert notification settings dropdown into groups

## Display notification settings dropdown for groups

part of #3359   

![groups](/uploads/d61648236b81b0cca55fa2d73758f0df/groups.png)
![Screenshot_from_2016-06-29_10-58-37](/uploads/7be05ea6002932c094a81b25a308fd62/Screenshot_from_2016-06-29_10-58-37.png)  
![small](/uploads/6f2b556d734c870e358f6f56618a0bab/small.png)

See merge request !4857